has been solved.
the solution is to reduce the less version to 1.6.2.
npm install less@1.6.2-g
command line executes the above code, restart sublime
create a new less file, Ctontrol+S save automatically generate compressed css file

change the less version command as follows npm install less@1.6.2-g I am so solved

according to the hint, is clean-css not installed

Brother problem solved? the same problem.

npm install less@2.7.3 -g

refer to https://github.com/less/less-.

https://www.cnblogs.com/xiang.

@ the taste of sunshine and @ good Dadong method are useful and solve my problem! Thank you! Specially login to like!